The Hilton Head Public Service District will borrow nearly $3 million to expand its reverse-osmosis plant on Jenkins Island, raising its water filtration capacity from 3 million to 4 million gallons a day and helping the water utility deal with contamination of freshwater wells.
The plant, built in 2009, draws brackish water from the Middle Floridan Aquifer -- about 600 feet below sea level -- and removes salt from it to provide potable water to customers on the island's north end
The $3.74 million in general obligation bonds -- authorized by Beaufort County Council on Monday -- would be paid for by property owners within the district over a period of 20 years at a 1.9-percent interest rate, according to district spokesman Pete Nardi
The owner of a home valued at $100,000 would pay an additional $2.88 in annual property taxes, or $30.40 a year, Nardi said. Residents could first see the increase on 2015 property tax bills, he said.
The state requires public service districts to get approval from county governments to issue bonds, according to county staff attorney Josh Gruber.
The bond would be used to pay for:
Saltwater plumes are advancing into the freshwater Upper Floridan Aquifer at a rate of about 400 feet a year from Port Royal Sound, Nardi said.
The aquifer, about 150-250 feet below sea level, is an underground limestone table that holds freshwater like a sponge and is replenished naturally. However, over-pumping in parts of South Carolina and Georgia -- particularly in Savannah -- are causing saltwater to seep in, according to the S.C. Department of Health and Environmental Control.
The district has lost six of its 12 Upper Floridan wells since 2000 and expects three of its remaining six to become unusable by 2017, Nardi said.
Expanding the plant's capacity makes up for those lost wells, Nardi said. This would be the first upgrade made to the plant's capacity, and it could eventually produce up to 6 million gallons a day, he said.
The cost of producing the water -- factoring in debt payments for the expansion -- is about $1.16-$1.18 per 1,000 gallons, Nardi said. Without considering those capital costs, processing the brackish water costs 65 cents per 1,000 gallons.
Nardi said losing more freshwater wells -- the cheapest source available, costing about $.45 per 1,000 gallons -- appears inevitable, so the district has been gradually incorporating alternative water sources.
In addition to getting water from the aquifer, the district buys water pumped from the Savannah River from the Beaufort-Jasper Water & Sewer Authority during most of the year for $1.58 per 1,000 gallons. The authority treats the river water that goes to the public service district.
In winter months, when the demand and price of the treated river water is reduced, the district stores water in mid-level aquifer wells, from which it can be drawn when demand peaks in the summer. That process costs about $.99 per 1,000 gallons.
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